JP3675124B2 - Control device for pulse width modulation control converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control apparatus for a pulse width modulation control converter that can avoid adverse effects due to generated harmonics even if the number of operating pulse width modulation control converters connected to an AC power supply changes.
[0002]
[Prior art]
AC power can be converted to DC power by connecting a pulse width modulation control converter to the AC power supply. If this DC power is input to the pulse width modulation control inverter, AC power with variable voltage and variable frequency can be obtained, and therefore the induction motor can be operated at a desired rotational speed with this AC power. Therefore, an electric vehicle that has conventionally used a DC motor can now be driven by an induction motor. Therefore, in the following, the present invention will be described by taking an AC electric vehicle running by converting AC power supplied from an overhead line by a pulse width modulation control converter and a pulse width modulation control inverter and driving an induction motor as an example. .
[0003]
FIG. 5 is a circuit diagram showing a conventional example of an AC electric vehicle that runs with two induction motors. In this conventional circuit, the AC power supplied from the overhead wire 1 is applied to the primary winding 3C of the transformer 3 via the pantograph 2 as a current collector, and then to the ground via the wheel 4 and the rail 5. It is released. This transformer 3 has two secondary windings 3A. 3B, and one secondary winding 3A is connected to a pulse width modulation control converter (hereinafter abbreviated as a PWM converter) 12 via a switch 11 to convert AC power input thereto into DC power. To do. A pulse width modulation control inverter (hereinafter abbreviated as PWM inverter) 13 connected to the PWM converter 12 converts the DC power from the PWM converter 12 into AC power having a desired voltage and frequency, and the induction motor uses this AC power. 14 is operated at a variable speed. Similarly to the above, the other secondary winding 3B is connected to the PWM converter 22 via the switch 21, and the PWM inverter 23 is connected to the PWM converter 22 to drive the induction motor 24 at a variable speed. These electric motors 14 and 24 allow the AC electric vehicle to travel at a desired speed.
[0004]
The gate control circuit 7 that inputs the carrier signal output by the carrier frequency generation circuit 6 converts the AC power into DC power by controlling the on / off of the converters 12 and 22 at an appropriate timing by pulse width modulation control. . The PWM inverters 13 and 23 also convert direct current into alternating current by pulse width modulation control using a separate carrier signal. However, the operation of the PWM inverters 13 and 23 is irrelevant to the present invention, and thus description of this part is omitted. .
[0005]
[Problems to be solved by the invention]
Harmonics are generated with the operation of the PWM converters 12 and 22 mounted on the aforementioned AC electric vehicle. If this harmonic flows through the overhead wire 1 or the rail 5, there is a risk that the electric equipment connected thereto will be damaged. For example, resonance of the power supply circuit, malfunction of the signal circuit, inductive disturbance to the communication equipment, and the like. These harmonic disturbances may impair safe driving of AC electric vehicles and must be avoided by all means.
[0006]
Therefore, as shown in the conventional circuit of FIG. 5, even if the carrier signals of the two sets of PWM converters have the same frequency, a phase difference is provided for each carrier signal, and the carrier signal frequency is appropriately selected. This avoids the generation of harmonics of frequencies that can cause disturbances. That is, assuming that the number of operating PWM converters is N, the frequency of the carrier signal is f _C , and the frequency of the AC power supply is f ₀ , the frequency f _{HH of the} harmonics generated when the carrier signal has a phase difference of π / N. Is represented by the following Equation 1. However, m and n are positive integers (m, n = 1, 2, 3...).
[0007]
[Expression 1]
f _HH = 2 · N · n · f _C ± (2 · m−1) f ₀
Since the conventional circuit of FIG. 5 operates two sets of PWM converters, N = 2. Therefore, if the carrier signal frequency f _C is selected to be higher than ¼ of the harmonic frequency that may cause a failure, the failure due to the harmonics up to four times the carrier signal frequency f _C can be avoided. .
[0008]
However, if any one of the two PWM converters in operation is stopped due to a failure or the like, N = 1 in Equation 1, so that the frequency f _HH of the generated harmonic is ½ of the previous one. Therefore, this may cause a harmonic disturbance.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to avoid generation of harmonics of a frequency causing a failure even when the number of operating PWM converters connected to an AC power supply is changed.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a control device for a pulse width modulation control converter of the present invention comprises:
A pulse width modulation control converter that converts alternating current to direct current by pulse width modulation control is connected to each of the secondary windings of the transformer via a separate switch, and each of the pulse width modulation control converters has a carrier. In a pulse width modulation control converter configured to give a carrier signal of a predetermined frequency from a frequency generator,
The number of operating pulse width modulation control converters is detected from the open / closed state of the switch, and a carrier signal having a frequency corresponding to the number of operating units is selected to control the pulse width modulation control converter.
[0010]
Alternatively, the number of operating pulse width modulation control converters is detected from the open / closed state of the switch, a carrier signal having a frequency corresponding to the number of operating units is selected, and a phase difference corresponding to the number of operating units is given to each carrier signal. To control the pulse width modulation control converter.
Alternatively, the number of operating pulse width modulation control converters is detected from the open / closed state of the switch, the carrier signal of the frequency corresponding to the number of operating units, and the maximum current limit value of the pulse width modulation control converter corresponding to the number of operating units And select the pulse width modulation control converter.
[0011]
Alternatively, the number of operating pulse width modulation control converters is detected from the open / closed state of the switch, a carrier signal having a frequency corresponding to the number of operating units is selected, and a phase difference corresponding to the number of operating units is given to each carrier signal. In addition, the maximum current limit value of the pulse width modulation control converter corresponding to the number of operating units is selected to control the pulse width modulation control converter.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a circuit diagram showing a first embodiment of the present invention, which corresponds to claim 1. This first embodiment circuit is different from the conventional circuit already described in FIG. And a selection circuit 32 are added. Therefore, the description of the part already described in the conventional circuit of FIG. 5 is omitted.
[0013]
In the circuit of the first embodiment, the carrier frequency generation circuit 31 outputs carrier signals having two different frequencies. That is, the carrier signal A1 has a frequency corresponding to the case where two sets of PWM converters are operating, and the frequency is selected so that the harmonics generated by the carrier signal A1 do not cause inconvenience. The point has already been explained. The carrier signal A2 is a frequency corresponding to the case where one of the PWM converters is stopped due to a failure or the like and only one unit is operated. As is clear from Equation 1, the frequency is the frequency of the carrier signal A1 described above. 2 times.
[0014]
The selection circuit 32 inputs the open / closed state of the switch 11 and the switch 21, selects one of the two carrier signals A 1 and A 2 output from the carrier frequency generation circuit, and supplies the selected signal to the gate control circuit 7. Therefore, when the number of operating units is one, by selecting the carrier signal A2, the frequency of the generated harmonics becomes the same as the case of two units, and obstacles due to the harmonics can be avoided.
[0015]
FIG. 2 is a circuit diagram showing a second embodiment of the present invention and corresponds to claim 2. This second embodiment circuit is different from the conventional circuit already described in FIG. And a phase difference changing / selecting circuit 41. Therefore, the description of the part already described in the conventional circuit of FIG. 5 is omitted. Since the carrier frequency generation circuit 31 has already been described in the circuit of the first embodiment of FIG. 1, the description thereof is also omitted.
[0016]
As described above, the phase difference changing / selecting circuit 42 selects a carrier signal having a frequency corresponding to the number of operating PWM converters, and provides a difference in the phase of the carrier signal applied to each PWM converter corresponding to the number of operating PWM converters. In this second embodiment circuit, the number of operating units is changed from two to one, so there is no need to consider the phase difference. For example, when the number of operating units is changed from four to three, each PWM converter The phase difference of the carrier signal is changed from π / 4 to π / 3.
[0017]
FIG. 3 is a circuit diagram showing a third embodiment of the present invention and corresponds to claim 3. This third embodiment circuit is different from the conventional circuit already described in FIG. The maximum current limit value generation circuit 51 and the selection circuit 52 are added. Therefore, the description of the part already described in the conventional circuit of FIG. 5 is omitted. The carrier frequency generating circuit 31 has already been described in the circuit of the first embodiment shown in FIG. 1, and the description thereof is also omitted.
[0018]
If the frequency of the carrier signal is increased, the number of times of switching per unit time of each semiconductor switch element constituting the PWM converter increases in proportion to this frequency. Along with this, the switching loss of each element also increases. Therefore, if the current flowing through the device is not limited as the carrier signal frequency increases, the total loss of the device may increase, leading to thermal destruction. Therefore, if the carrier signal frequency increases from A1 to A2 as the number of operating PWM converters is changed, the maximum current limit value of the element is changed from B1 to B2. The selection circuit 52 inputs the open / close state of the switches 11 and 21 and selects the maximum current limit value of the element together with the carrier signal frequency.
[0019]
FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention, which corresponds to claim 4. The circuit of the fourth embodiment is different from the conventional circuit already described in FIG. The maximum current limit value generating circuit 51 and the phase difference changing / selecting circuit 62 are added. Therefore, the description of the part already described in the conventional circuit of FIG. 5 is omitted. Since the carrier frequency generation circuit 31 has already been described in the circuit of the first embodiment of FIG. 1, and the maximum current limit value generation circuit 51 has been described in the circuit of the third embodiment of FIG. .
[0020]
As described above, the phase difference changing / selecting circuit 62 selects a carrier signal having a frequency corresponding to the number of operating PWM converters and a maximum current limit value, and corresponds to the number of operating carrier signals in phase. Make a difference.
[0021]
【The invention's effect】
When a plurality of PWM converters are operated by providing a carrier signal with a phase difference, harmonics having a frequency corresponding to the number of the operated PWM converters are generated. An appropriate value is selected for the frequency of the carrier signal so that this harmonic does not adversely affect other electrical equipment, but if the number of operating PWM converters changes due to a failure or the like, the frequency of the generated harmonic will be reduced. It may change and cause damage to electrical equipment. Therefore, in the present invention, the number of operating PWM converters is detected from the open / closed state of a switch provided on the power supply side of each PWM converter, and the frequency of the carrier signal is changed in accordance with the number of the PWM converters. Or at the same time, the phase difference of the carrier signal applied to each PWM converter is also changed. Thereby, the effect which can suppress that the harmonic of the frequency which has a bad influence on another electric equipment generate | occur | produces is acquired.
[0022]
In addition, if the carrier signal frequency is increased by decreasing the number of operating PWM converters, the loss of the switching element increases. Therefore, reducing the maximum current limit value of the element as the number of operating units decreases may cause the element to be thermally destroyed. Effects that can be avoided are also obtained.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment of the present invention. FIG. 2 is a circuit diagram showing a second embodiment of the invention. FIG. 3 is a circuit diagram showing a third embodiment of the invention. 4 is a circuit diagram showing a fourth embodiment of the present invention. FIG. 5 is a circuit diagram showing a conventional example of an AC electric vehicle driven by two induction motors.
DESCRIPTION OF SYMBOLS 1 Overhead line 2 Pantograph 3 Transformer 3A, 3B Secondary winding 4 Wheel 5 Rail 6, 31 Carrier frequency generation circuit 11, 21 Switch 12, 22 PWM converter 13, 23 PWM inverter 14, 24 Induction motor 32, 52 Selection circuit 42 62 Phase difference change / selection circuit 51 Maximum current limit value generation circuit

Claims (4)

An AC power source is connected to the primary winding of a transformer having a plurality of secondary windings, and each secondary winding is converted to DC by pulse width modulation control via a separate switch. In a pulse width modulation control converter configured to connect a pulse width modulation control converter and supply a carrier signal of a predetermined frequency from a carrier frequency generator to each pulse width modulation control converter,
A carrier frequency generation circuit for generating a carrier signal having a frequency corresponding to the number of operating pulse width modulation control converters, and a carrier having a frequency corresponding to the number of operating pulse width modulation control converters detected from the open / closed state of each switch A control device for a pulse width modulation control converter, comprising: a selection circuit that selects a signal. An AC power source is connected to the primary winding of a transformer having a plurality of secondary windings, and each secondary winding is converted to DC by pulse width modulation control via a separate switch. In a pulse width modulation control converter configured to connect a pulse width modulation control converter and supply a carrier signal of a predetermined frequency from a carrier frequency generator to each pulse width modulation control converter,
A carrier frequency generation circuit for generating a carrier signal having a frequency corresponding to the number of operating pulse width modulation control converters, and a carrier having a frequency corresponding to the number of operating pulse width modulation control converters detected from the open / closed state of each switch A control apparatus for a pulse width modulation control converter, comprising: a phase difference changing / selecting circuit that selects a signal and gives a phase difference corresponding to the number of operating units to the carrier signal. An AC power source is connected to the primary winding of a transformer having a plurality of secondary windings, and each secondary winding is converted to DC by pulse width modulation control via a separate switch. In a pulse width modulation control converter configured to connect a pulse width modulation control converter and supply a carrier signal of a predetermined frequency from a carrier frequency generator to each pulse width modulation control converter,
A carrier frequency generating circuit for generating a carrier signal having a frequency corresponding to the number of operating the pulse width modulation control converters, and limiting a maximum current of the pulse width modulation control converter corresponding to the number of operating pulse width modulation control converters; A maximum current limit value generating circuit; and a selection circuit for selecting a carrier signal having a frequency corresponding to the number of operating pulse width modulation control converters detected from the switching state of each switch and a maximum current limit value. A pulse width modulation control converter control device. An AC power source is connected to the primary winding of a transformer having a plurality of secondary windings, and each secondary winding is converted to DC by pulse width modulation control via a separate switch. In a pulse width modulation control converter configured to connect a pulse width modulation control converter and supply a carrier signal of a predetermined frequency from a carrier frequency generator to each pulse width modulation control converter,
A carrier frequency generating circuit for generating a carrier signal having a frequency corresponding to the number of operating the pulse width modulation control converters, and limiting a maximum current of the pulse width modulation control converter corresponding to the number of operating pulse width modulation control converters; Select the maximum current limit value generation circuit and the carrier signal and the maximum current limit value of the frequency corresponding to the number of operating pulse width modulation control converters detected from the open / closed state of each switch, and the level corresponding to the number of operating units. A control device for a pulse width modulation control converter, comprising: a phase difference changing / selecting circuit for giving a phase difference to the carrier signal.

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